Driver side or passenger side supplemental inflatable restraint (SIR) systems typically include an air bag stored in a housing module within the interior of the vehicle in close proximity to either the driver or one or more passengers. SIR systems are designed to actuate upon sudden deceleration so as to rapidly deploy an air bag to restrain the movement of the driver or passengers. During deployment, gas is emitted rapidly from an inflator into the air bag to expand it to a fully inflated state.
Air bag passive restraint systems include an inflator, which produces gas to inflate the air bag cushion. Known inflators for air bag modules are generally of three types. One type is the pure gas inflator wherein a pressure vessel contains stored pressurized gas. The pressure vessel communicates with the cushion through various types of rupturable outlets or diaphragms. Another type is the gas generator wherein a propellant is ignited and the resultant gas created flows through an outlet to the cushion. A third type is the hybrid or augmented type. This type includes a pressure vessel containing stored pressurized gas and a gas generator. When the generator is ignited, the resultant gas flows with and heats the stored gas going to the cushion through the pressure vessel outlet.
It is also known to inflate the cushion at a relatively low rate under low level deployment conditions, such as a sudden low level deceleration, and at a relatively high rate under high level deployment conditions, such as a sudden high level deceleration. Devices are known which provide primary inflation (reduced inflation) and full level inflation using a single gas vessel with two separate gas heaters. Primary inflation is accomplished by actuating the gas vessel and heating the gas at a specified reduced level. Full level inflation is accomplished by actuating a second separate heater located at the bottom of the gas vessel to heat the gas at a greater level. This second heater is deployed at the same time or a delayed time as the primary heater to provide full level inflation. It is also known in the art to use a system having two discrete inflators to accomplish dual level inflation. In these types of systems, two discrete inflators are deployed at the same time or at a delayed time depending upon the severity of the sudden deceleration.
It has also been suggested in the prior art to provide an air bag module including a reaction canister which houses the inflator and air bag and which includes a valve member which is continually repositioned for opening, closing, or partially opening the vent openings on the reaction canister primarily in response to changes in ambient temperature by the use of a bimetallic spring, servo motor or solenoid valve. Thus, the amount of the discharging inflator gas expelled from the housing is controlled solely by the exact position of the valve member which must be carefully positioned for providing partial opening of the vent openings. In addition, the prior art teaches that the position of the valve member and the amount of venting is continually adjusted during vehicle use prior to activation of the inflator rather than only specifically at the time of air bag deployment. In addition, the use of a bimetallic spring, servomotor, or solenoid takes time to move the valve member between the various positions and thus is continually being adjusted prior to activation of the inflator. This arrangement is also complex and adds mass to the module.